变温反相悬浮聚合制备温度敏感性聚合物微凝胶

报道了一种利用变温的途径制备具有温度敏感性聚合物凝胶微粒的悬浮聚合方法.以正庚烷为连续相,过硫酸铵和四甲基乙二胺为引发剂,采用将具有反向温敏性的可降解大分子单体水溶液在低温下分散好以后再升高到聚合温度的变温反相悬浮聚合的方法制备了反向温敏性的可降解微凝胶.该方法避免了由于分散相在聚合温度下发生物理凝胶化所导致的分散困难等问题.考察了微凝胶的温敏性、粒径分布和降解行为等,并研究了油水比对微凝胶形貌的影响.

PREPARATION OF THERMO-SENSITIVE POLYMER MICROGELS BY ALTERED-TEMPERATURE SUSPENSION POLYMERIZATION

An altered-temperature inverse suspension polymerization,which was suitable for negatively thermosensitive macromers,was presented to prepare thermosensitive and biodegradable microgels.The thermosensitivity and biodegradability of microgels come from those of macromers.The microgels were synthesized in suspension,in which the continuous phase was heptane.Ammonium persulphate and N,N,N′,N′-tetramethylethylenediamine were employed as the initiating system.The negatively thermosensitive macromer aqueous solution was first dispersed well at low temperatures(lower than the sol-gel transition temperature of the macromer solution) and then crosslinked after raising temperature.The highlight of this approach is the avoidance of dispersion difficulty of the dispersion phase because of its physical gelation at polymerizing temperature.The thermosensitivity and biodegradation of the resulting microgels were confirmed.The volume phase transition temperature of microgels was around 25℃,and the volume of microgels at 37℃ was less than half of that at 4℃.Microgels were completely degraded into water-soluble products.It was necessary to add aqueous solutions of initiator and accelerator into the continuous phase after raising temperature.The ratio of oil to water influenced the morphology of microgels to a certain degree.